The present invention relates to a toroidal type continuously variable transmission (CVT), and more specifically to a loading cam mechanism for producing an axial thrust load in accordance with an input torque.
Japanese Patent Provisional (Kokai) Publication No. 63-106456 shows a conventional example. A toroidal type transmission of this example has a center transmission shaft, input and output discs which are mounted on the center shaft and which form a toroidal cavity therebetween, and friction rollers which are installed in the toroidal cavity for transmitting torque between the input and output discs, and which are inclined to continuously vary a transmission ratio. In order to prevent slippage of the friction rollers, there is further provided a loading cam mechanism for producing an axial thrust load in accordance with an input torque, and applying the axial thrust load on one of the input and output discs so as to push one toward the other.
As shown in FIG. 5, the loading cam mechanism 1 of this conventional example includes a drive plate 3 mounted on the center transmission shaft 2 at the side of the input disc 4, and cam rollers 5 confined between cam surfaces 3a and 4a of the drive plate 3 and the input disc 4. The drive plate 3 is splined to the center shaft 2, and an axial movement of the drive plate 3 is limited by an outward flange of the center shaft 2. When the input torque is varied, the drive plate 3 and the input disc 4 rotate relative to each other, and the cam rollers 5 roll on the cam surfaces 3a and 4a and varies the axial thrust load applied on the input disc 4 by varying the axial distance between the drive plate 3 and the input disc 4.
The drive plate 3 is formed with at least one radial oil hole 6 for carrying a lubricating oil discharged from a radial hole 7 of the center shaft 2, to the cam rollers 5. The lubrication of the cam rollers is very important in order to ensure the smooth and accurate operation of the cam mechanism.
In this conventional loading cam mechanism 1, however, the lubrication is not satisfactory. Each cam roller 5 is rotatable relative to the drive plate 3. Therefore, the oil hole 6 is not always held at a position appropriate to direct the oil to the cam roller 5, and the lubrication becomes insufficient when the oil hole turns aside from the cam roller 5. The shortage of the lubricating oil causes wear and seizure in the cam rollers 5 and the cam surfaces 3a and 4a.